Sharpness at 24mm

Our sharpness tests are carried out by photographing a real-world subject rather than a test chart. The Tamron 20-40mm F/2.8 Di III VXD was attached to a Sony A7R IV camera, which in turn was mounted on a sturdy tripod. Self-timer mode was activated to steady the camera completely. Any slight tonal changes you may see across the crops are a result of slight changes in natural light during the shooting session.

The full frame at 24mm

Centre sharpness remains impressively high through from f/2.8-f/11, with f/16 and especially f/22 being affected by diffraction.

The edges aren't quite as sharp as the centre, with f/4-f/11 producing the sharpest results.

Aperture	Centre Crop	Edge Crop
f/2.8
f/4
f/5.6
f/8
f/11
f/16
f/22